ACP 11 has your answers. From the wording here, I believe you can join the CWC at 18, so long as you are no longer a cadet.
Ineligibility. No person may be appointed to any role within the Squadron Committee if:
a. They are VR(T) Officers, Adult WOs or SNCOs, Chaplains, Civilian Instructors, cadets and other young people under the age of 18 years. The Officer Commanding and Squadron Chaplain are ex-officio members but with no voting rights.
I however would question what you mean by “I’m currently a Staff Cadet FS and it feels like my time is now up in the uniform side of things.”
Is it that you can no longer commit the time, but want to still be involved? As if you can still commit the time I would assume you can have a better impact as a Cadet FS than you could as a CWC member.
That honestly sounds like a fair solution then. I would wonder however that a chat with your OC may change things. They might be more than willing to keep you on as a cadet even if you can’t attend as often. At the end of the day you’re a staff cadet and if there’s something you are offering to your unit that other staff can’t really cover, then I’d personally just keep you on the books as an SNCO. For example if you’re the only one who teaches comms or something.
I have not! But yes, the wording certainly seems to be that it is okay.
Lots of staff cadets can’t attend as much as they used to be able to, it’s generally accepted. If I was you - and I was in the position a few years ago - I’d consider staying as a Staff Cadet but attending less so you can still get something out of the organisation.